In this proposal, the role and mechanism of melanin-concentrating hormone (MCH) in the regulation and function of the lateral hypothalamus (LH) at the cellular level will be addressed. In feeding regulation LH plays a key role and has been considered as a feeding center. The regulation of food intake is crucial in energy- balance homeostasis. Unbalanced energy accumulation leads to obesity. MCH is a cyclic 19-amino-acid peptide. A substantial body of evidence from systemic, morphological and molecular biological studies suggests that MCH is involved in feeding regulation. However, there is little evidence as to the physiological role of MCH in LH neurons at the cellular level. Also there is little evidence as to how MCH and other neuropeptides interact in LH neurons. Furthermore, there is little data about the cellular physiology as well as properties of neurons and neuronal organization in the LH area. In this proposal, electrophysiological methods (including extracellular recording, whole-cell voltage and current clamp recording), immunocytochemistry and digital calcium imaging will be employed in cultured neurons and acute hypothalamic slices from rats. The chief hypothesis to be tested is that MCH acts as an inhibitory neuropeptide to modulate neuronal activity in the LH. The following hypotheses will be examined: 1. MCH depresses the activity-dependent gene transcription. 2. MCH inhibits the function of voltage-dependent calcium channel subtypes via distinct signaling pathways. 3. MCH depresses glutamatergic and GABAergic synaptic transmission in the LH slices. 4. Characterization and organization of MCH responding neurons in LH slices will be documented. This proposal will begin to bridge the gap between molecular research and systemic studies on the regulation of feeding to benefit those suffering from obesity and obesity-related diseases. The applicant's previous work in characterizing the cellular physiology of the newly discovered neuropeptide hypocretin/orexin is the first step in his journey to pursue his long-term goal of understanding neurotransmission in the LH. The funding of this research proposal is important for the applicant to continue this course. A career development plan is also documented in this proposal.